Fluid Statics

Hydrostatic pressure is the pressure a fluid exerts onto an underwater structure (be it a pool wall, a container wall, a ship, etc.). Pressure is equal to force per unit area \left(\frac{F}{A}\right) and has the following behaviors:

Pressure is linearly related to the vertical depth of the object

Pressure is independent of the size and shape of the container that holds it (only depth and density factors into determining the hydrostatic pressure acting on an object)

A pressure at any given point will have the same magnitude in all directions (this is referred to as Pascal's Law).

Since fluids are not capable of supporting any shear stress, the pressure exerted on a submerged object will always be normal to the object's surface (See Figure 1)

Fluid Pressure

Liquids can be assumed to have constant density over fairly large vertical distances. The same can be said of gases although only over small distances. Given that the pressure of the fluid body is zero at its surface, the pressure at any point below the surface is easily calculated as: